<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script>
			// var x = 10;
			// console.log( x );  //10
			
			// {  //代码段
			// 	var x = 100;
			// 	console.log( x );  //100
			// }
			// console.log( x ); //？10？100
			
			//es6的新标准，变量
			let x = 10;
			console.log( x );
			{
				let x = 100;
				console.log(x);
			}
			//代码段中let定义变量作用域，代码段结束，里面的x也结束
			console.log(x);
			
			//js只有变量没有常量定义，es6定义常量
			const sysname = "学生管理系统";
			console.log(sysname);
			//sysname = "mis";
			//console.log(sysname);
			
			const PI = 3.14;
			console.log(PI);
			PI = 3.1415926;
		</script>
	</head>
	<body>
		<h3>es6新标准案例</h3>
	</body>
</html>
